Structural analogues of quinoline alkaloids: Straightforward route to dioxoloquinolines with antibacterial properties

Compounds bearing [1,3]dioxolo‐quinoline scaffolds have been found in quinoline‐based natural products; the only exception is the [1,3]dioxolo[4,5‐c]quinoline moiety with a rare occurrence in both natural and synthetic derivatives. In this article, we report the preparation of diversely substituted and functionalized [1,3]dioxolo[4,5‐c]quinolines using [1,3]dioxolo[4,5‐c]quinoline‐4‐carbaldehyde (DQC) as the common intermediate. DQC was synthesized on a large scale from anthranilic acid and chloroacetone as the starting materials, with the rearrangement of acetonyl‐anthranilate as the key step. The developed method allows for the simple preparation of [1,3]dioxolo[4,5‐c]quinolines with various C2 substituents on the quinoline scaffold. Additionally, the synthetic route was successfully applied to the preparation of 3‐hydroxyquinoline‐4(1H)‐ones. The target compounds were tested against representative Gram‐positive/negative bacteria, and two derivatives exhibited submicromolar minimum inhibitory concentrations against Micrococcus luteus.